[7ontheline]

I think raising is bad here - you'll likely only fold out hands you have dominated, or are at least ahead of, and not really improve your chances all that much. Assuming CO's donk means he has something (pair, draw) then you'll probably be better folding. You could easily be drawing dead or very thin, and your outs are pretty dirty. Lots of hands will have redraws on you should you hit your best possible card (non-diamond K) on the turn. If there were any spades in the flop I would call. It's a big pot though, if you knew for sure no one behind you would raise the flop then a peel is probably OK.